The present invention relates to ether modified polyesterimide resins and to substrates such as electrical conductors coated therewith. More particularly, the present invention relates to ether modified polyesterimide resins which are substantially free of inert solvents and which exhibit improved properties.
Polyesterimide resins have typically been prepared from a lower dialkyl ester of terephthalic acid or isophthalic acid, ethylene glycol, a saturated aliphatic polyhydric alcohol having at least three hydroxyl groups, a diamine, and a tricarboxylic anhydride or tetracarboxylic dianhydride which will react to produce imide groups within the polyester structure, using syntheses wherein inert solvents are employed. As used herein, "inert solvents" and terms of similar import means solvents which do not react with monomeric reactants from which polyesterimide resins are synthesized. Such syntheses have not been entirely satisfactory due to the high costs of solvents and increasingly stringent governmental regulations on emissions and disposal thereof.
Attempts to carry out such polyesterimide synthesis in the absence of inert solvents have not been completely successful due to the fact that the lower dialkyl phthalate esters undergo sublimation from the reaction mixtures, resulting in deposition of flow-hindering solid deposits in conduits provided for recovering by-product vapors released from the reacting mixtures, deviations from the preselected relative amounts of reactants in the reacting mixtures, and other problems. Moreover, in the absence of a solubilizing amount of inert solvent, rapid increases in resin viscosity in later stages of the synthesis undesirably occur. This creates additional control problems including, in some instances, gelling of the resin in the synthesis vessel.
Precopio et al., U.S. Pat. No. 2,936,296, discloses a process for preparing polyester resins from dimethyl, terephthalate, ethylene glycol, and a saturated aliphatic trihydric alcohol, wherein the reaction is carried out with xylene or a similar material added to the reaction mixture for the stated purpose of preventing sublimation of the dimethyl terephthalate. As described therein, the added material takes no part in the reaction.
Meyer, U.S. Pat. No. 3,426,098, teaches the preparation of polyesterimides by reacting in an inert solvent tris (2-hydroxyethyl) isocyanurate, a polycarboxylic acid, an aromatic diamine, and an aromatic carboxylic anhydride containing at least one additional carboxyl group. According to Meyer there are usually employed about 2 moles of anhydride per mole of amine.
Payette, U.S. Pat. No. 3,567,673, teaches that polyesterimide resins can be prepared by substituting for a part of the phthalate moiety, an imide group producing constituent. This can be accomplished by including in the polyester ingredients a primary amine and a tricarboxylic anhydride or tetracarboxylic dianhydride which will react to produce imide groups within the polyester structure. Alternatively, the imide group producing material can be prepared separately by first reacting the primary amine and the anhydride to produce a diamino diacid material which can then be reacted with the other polyester ingredients. The polyesterimide ingredients are reacted in a suitable solvent such as cresylic acid, cresylic acid-phenol mixtures, and the like, with or without the addition of high boiling hydrocarbon solvents.
Keating, U.S. Pat. Nos. 4,119,605, 4,119,608 and 4,119,758, describes polyesterimide resins wherein during the formation of the polyesterimide there is employed as a reactant either an ether of the formula RO(C.sub.n H.sub.2n O).sub.x H, where R is an alkyl group of 1 to 6 carbon atoms or phenyl, n is 2 or 3 and x is 2 or 3, or the monophenyl ether of ethylene glycol or mixtures of such monoethers. It is stated therein that the use of the monoether of a glycol as a reactant which serves as a monofunctional alcohol serves to control the molecular weight and solubility of the polymer and permits the manufacture of wire enamels which contain relatively non-toxic solvents in place of phenols, and also permits the attainment of enamels having economical high solids content. While reacting the ether alcohol into the resin controls its molecular weight and improves its solubility, it also tends to reduce ultimate physical properties.
Boldebuck et al., U.S. Pat. No. 4,233,435, found that the problems associated with preparing polyesterimide resins free of inert solvents from lower dialkyl esters of terephthalic acid or isophthalic acid can be eliminated to a substantial extent by including in the reaction mixture an organic component containing monohydric alcohol functionality, for example, n-hexanol, 2-ethylhexanol, n-nonanol, n-decanol, n-dodecanol, tetrahydrofurfurol, 2-butyloctanol, tetradecanol, 2,6,8-trimethylnonane-4-ol, and the like. It is disclosed therein that suitable anhydrides for making the polyesterimides include, in some instances alone, but preferably in admixture with trimellitic anhydride, 2,2-bis[4-(3,4-dicarboxyphenoxy) phenyl] propane dianhydride; i.e. 4-BPADA, and 2,2-bis[4-(2,3-dicarboxyphenoxy) phenyl] propane dianhydride; i.e. 3-BPADA. For best results, the total weight of such anhydrides is limited to an amount corresponding to up to about 1.0 imide groups formed therefrom per total moles of the trimellitic anhydride.
Zamek, U.S. Pat. No. 4,267,231, is based on the discovery that when polyesterimide resins are prepared in the presence of a monobutyl ether of a partially linear, partially branched aliphatic diglycol having two carbon atoms in one portion and three carbon atoms in the other portion of the aliphatic chain, and in which the monohydric alcohol group is a secondary alcohol group, then there is little tendency for the glycol ether to react into the resin, and consequently the molecular weight is higher than it would be if a glycol ether of the type described in the foregoing Keating patents was employed.
Zamek et al., U.S. Pat. No. 4,269,752, is similar to the foregoing Zamek U.S. Pat. No. 4,267,231 in that it is based on the discovery that when polyesterimide resins are prepared in the presence of a monophenyl ether of a branched aliphatic glycol having at least three carbon atoms in the aliphatic chain and in which the monohydric alcohol group is a secondary alcohol group, then there is little tendency for the glycol ether to react into the resin, and the molecular weight is higher than it would be if a glycol ether of the type described in the Keating patents was employed.
Bolon et al., U.S. Pat. No. 4,307,226, teaches that polyesterimide resins which are readily soluble in solvents such as monoethers of glycols are prepared by incorporating into the preformed polyesterimide resin an effective amount of ethylene glycol. By means of a transesterification process, the ethylene glycol becomes part of the polyesterimide molecule, thereby forming a polyesterimide resin which is soluble in such solvents. As in Meyer, the molar ratio of anhydride to amine is about 2:1.
Lee and Zamek, U.S. Pat. No. 4,354,965, discloses polyetheramideimide resins prepared by polycondensation of bisphenol-A dianhydride (e.g. BPADA), a tribasic acid anhydride, a diisocyanate and/or diamine in an inert solvent.
All of the foregoing patents are incorporated by reference in their entireties into the present disclosure.
It has now been discovered that aromatic bis (ether dianhydride) modified polyesterimide resins can be prepared by a process substantially free of inert solvents so as to provide ether modified polyesterimide resins which exhibit properties substantially equivalent to polyesterimide resins prepared by processes which utilize inert solvents.